A substrate supporting film to be etched is held on a rotating stage. Ultraviolet light having a wavelength of 200 nm or shorter radiated from first lamps irradiates the film in air, thereby removing an organic coatings from the film and making the surface of the film hydrophilic. A chemical solution is applied to the hydrophilic film while rotating the substrate. Ultraviolet light having a wavelength longer than 200 nm is radiated from second lamps and onto the film through the chemical solution.